“The agreement was finalized after a research period in which Stratolaunch charged Orbital with developing a comprehensive operational concept for its air-launch system, including the unique design of the rocket and operational processes and procedures that will need to be in place to operate the system,” the Stratolaunch release states, but offers no other information about the vehicle that Orbital will develop. The web site does indicate that the rocket, creatively called the Air Launch Vehicle (ALV), “combines proven solid and liquid propellant technology” and “utilizes a proven winged configuration first proven with Orbital’s patented Pegasus air-launch system and makes use of Orbital’s proven MACH avionics system, engineering standards and common vehicle and payload integration processes.” The video above shows what appears to be a mix of solid- and liquid-propellant engines used in the lower and upper stages, respectively, although one should be careful about reading too much into a single video.